- The Amateur Yacht Research Society

CATAMARANS 1959
A.Y.R.S.
PUBLICATION
No.
28
T H A I III
CONTENTS
1.
2.
3.
4.
5.
6.
7.
8.
8.
10.
Introduction
Manoeuvrability
Lee Bow Burying
One of a Kind Races
T H A I III
The PI-CAT
TIGER CAT
COUGAR
W I L D C A T II
C H I Q U I T A II
P R I C E
50
cents
II.
12.
13.
14.
15.
16.
17.
18.
18.
20.
SNAP
WINDCAT
ATTUNGA
SWIFT
SHAMROCK
HURRICANE
TAMAHINE
The C A T A M A N N E R S
A Retractable Undercarriage
SCAT
P R I C E
2/6
T H E A M A T E U R Y A C H T RESEARCH SOCIETY
(Founded June, 1955)
Presidents :
British :
American :
L o r d Brabazon of Tara, G.B.E.
Walter Bloemhard.
M . c , P.c.
Vice-Presidents
UfTa Fox,
:
American
New Y o r k
Victor Tchetchet.
W i l l i a m R. MehafTey
Great Lakes
Lloyd L . Arnold.
M i d West
Florida : Robert L . Clarke.
California : Joseph J. Szakacs.
British :
R.D.I.
D r . C. N . Davies, D.sc.
A u s t i n Farrar, M . I . N . A .
Erick J. Manners.
Committee :
British : Owen D u m p l e t o n , M r s . Ruth Evans,
L . Lamble, Roland Prout, Henry Reid.
Secretary- Treasurers
J. A . Lawrence,
:
British :
American :
T o m Herbert,
25, Oakwood Gardens,
Seven Kings,
Essex.
M r s . Yvonne Bloemhard.
143, Glen Street,
Glen Cove,
New Y o r k .
New Zealand :
South African :
Australian :
Charles Satterthwaite,
P.O. Box 2491,
Christchurch,
New Zealand.
Brian Lello,
S.A. Yachting,
58, Burg Street,
Cape T o w n .
K e n Berkeley,
75, Highfield R d . ,
Sydney,
N.S.W.
.
British
Research
Secretary
M r s . Ruth Evans,
^ ;
15, Westmorland Road,
Maidenhead,
Berks.
Editor
and Publisher
:
John M o r w o o d ,
Woodacres,
Hythe,
Kent.
Amateur Yacht Research Society
BCM AYRS
London
WCIN 3XX UK
www.ayrs.org
office@ayrs .org
Contact details 2012
;
.
EDITORIAL
•
,
- ,
,
>
;f
December, 1959.
T h e A . G . M . of the British A . Y . R . S . w i l l again be held at " T h e
Cedars," N o r t h l u i d Ro;id, near I'.arls Court on the first Saturday of
the Boat Show, the 2iul J;inuary, 1959 at I I a.m., (inishing at
p.m.
L i g h t refreshment w i l l be available. Matters for the Agenda can
be sent to T o m Herbert now. I t is requested that as many of the
aerodynamic and architectural members as possible w i l l attend as
the matter of greatest importance w i l l be the structure o f the w i n d
tunnel and whether or not to have a test tank. I t is most important
that the H o n . Editor shall have as much advice as possible before
erection starts.
THE
BOAT SHOW
Members are again reminded that our stand at Earls Court is
No. P3. M r s . M o r w o o d still needs help and offers o f this w i l l be
much appreciated.
SAILING TECHNOLOGY LECTURES
Erick Manners w i l l again be giving a series o f lectures at the
M u n i c i p a l College, Southend, Essex, starting i n January, 1960. Sixtysix people attended last year and more are likely to attend this year.
T h e subjects include : T h e o r y o f Sailing, Progress i n Sail, Outriggers,
Naval Architecture, Sail Design, Catamaran Research, Design, C o n struction and Sailing, H i g h Speed Boating, Trimarans, Hydrofoils,
Sailing Aerodynamics and Hydro-Mechanics. Erick has made a
film of eight different catamarans sailing w h i c h lasts three quarters
of an hour. T h i s w i l l be shown and it can also be obtained by Yacht
Clubs for their winter programmes.
INTRODUCTION TO CATAMARANS
1959
T h e fastest catamaran in the world at the moment for her size
is undoubtedly T H A I H I , designed by Roderick Macalpine-Downie.
T h i s was shown in the British O N E - O F - A - K I N D races where this
craft beat Donald Robertson's larger F R E E D O M i n 3 of the 6 races,
boat for boat w i t h the Prouts' C O U G A R S 3rd and 4th. T h i s result
was achieved by extreme lightness, good design and, of course, excellent
helmsmanship by John Fisk. Early this year, Roderick M a c A l p i n e Downie was hoping to b u i l d the present T H A I I I I to weigh ZOOlbs.
complete w i t h rigging but the final figure of weight is not yet k n o w n ,
though this figure has nearly been achieved.
,
Catamaran Hull Design. T i i i s has now settled into a shape which
is not likely to be much improved i n the forseeable future. T H A I I l l ' s
h u l l is not greatly different from D o n Robertson's F R E E D O M , the
main difference being a slightly lower transom and more V ' d sections
and an overhang forward, reminiscent of Bob Harris's Ocelot, shown
in A . Y . R . S . N o . 10 A M E R I C A N C A T A M A R A N S .
For the guidance o f catamaran designers, and to give credit to
the people who have not only designed nicely shaped catamaran hulls
but have been public spirited enough to allow their lines to be published,
the following designs seem to have all the essentials for speed : F R l ' ^ v
D O M by D o n Robertson. A . Y . R . S . N o . 22, page 20. T E M P E S T by
J. Fenwick. A . Y . R . S . N o . 22, page 44. T h i s catamaran never has
done well in any races due to her heavy weight from fibreglass construction but, i f made light enough she w o u l d perform well.
G O L D E N M I L L E R by M i c h a e l Henderson whose lines are
given opposite.
T h i s is o f course, a cruising catamaran w i t h fin and
bulb keels but the h u l l shape is that w h i c h w o u l d give a small racing
catamaran speed, i f built lightly.
T R I D E N T by W i l l i a m Baur whose lines are also given here.
T h i s is a largish cruising trimaran h u l l but the lines are so like those of
T H A I H I that there can be no doubt that great speeds w i l l be inherent
in them.
T w o further catamarans must be mentioned as having nicely
shaped hulls but both are light weather craft, i n m y opinion, and,
though possibly faster i n airs w o u l d not show the same top speeds.
V E L O C E C A T A M A R A N by L . Le Marrec of M o n t e CarloA . Y . R . S . N o . 22 page 40. S E A T O N I C by Eric Seaton A . Y . R . S .
No. 27 C R U I S I N G C A T A M A R A N S . T h i s again is a large craft
w i t h lines suitable for a small racing catamaran but the fineness aft
and counter would limit tiie top speeds.
4
I
THE
C O U G A R , S H E A R W A T E R H I and SW I F T C A T A M A R A N S
Readers w i l l naturally want to k n o w how the Prout range o f
racing catamarans w i l l compare w i t h those mentioned above.
The
answer lies in durability, weight and helmsmanship, not really i n the
hull design.
A C O U G A R , S H E A R W A T E R I I I or S W I F T is unlikely to
break when sailed hard over a season and is relatively light for its
durability. I f one of the above mentioned catamarans were of the
same weight as its relative member of the Prout scries, a race between
the two would go to the better helmsman. However, one cannot
but think that the finer bows and flatter runs aft of most o f the craft
mentioned above must help them at speed compared w i t h the P r o u t
series, though i n actual racing this has never been apparent as the
craft w h i c h have beaten the Prout craft have nearly always been
lighter in weight. A t speeds of 8 to 12 knots or thereabouts, the
S H E A R W A T E R H I or C O U G A R have less resistance than all others.
...
JUMPAHEAD
.
...
T h i s catamaran, designed by Bill O ' B r i e n doesn't fit into the
picture easily as it is a chine catamaran w i t h a very fine bow and very
flat run and wide transom. Its speed is, i f anything, only the barest
fraction worse than S H E A R W A T E R H I but it carries more sail
area. One can say that the h u l l resistance is definitely greater than
that of S H E A R W A T E R H I as it is the same weight.
i 'f.vU.,.
CATAMARAN
MANOEUVRABILITY
I t has now been clearly shown that, w i t h shallower hulls of
rounded section, cut away forefoot, flat and shallow transom and
•concentration of weight, buoyancy and wetted surface just aft o f
amidships, a catamaran can be put about as quickly as one wishes.
T h i s makes the need for full Ackerman linkage o f the rudders, as
•described in N o . 22, page 12, unnecessary.
LEE
BOW^ B U R Y I N G
T h e theory of this has not been fully worked out as yet. However,
some definite facts emerge from the accounts which have been sent
in. T h e first of these is that almost without exception, the catamarans
•with a Cat or U n a r i g and the mast placed well forward as it must be
to get sail balance, b u r y their lee bow. O n conversion to a sloop
rig, this stops. T o o much weight forward has the same effect, w h i c h
7
is the main reason for not deciding between the liuils right to the bows,
though decking in this part causes resistance from the waves hitting
underneath and from the w i n d .
F r o m the foregoing, it looks like being a matter of weight only
being too far forward but the 40 to 601bs. of the r i g being a couple o f
feet different could be balanced by the crew sitting a few inches further
back. Another explanation is that this displacement of the moments
of weight fore and aft makes the craft more stable i n pitch and so the
craft tends to go through waves, rather than rising over them.
Hull ExplaiKilions.
O n reaching its top speed, any dingiiy or
catamaran w i l l bury its bow and t i p up forward due to the centre o f
effort of the sails being high up. T h i s w i l l hold even w i t h planing
dinghies whose bows have to be held up by the weight of the crew
coming aft. However, dinghies seldom reach this state as a sideways
capsize w i l l usually occur first. Catamarans, due to their relatively
great lateral stability, w i l l easily get to this state and it is the fore and
aft stability which limits a catamaran's speed, rather than the lateral
stability, as pointed out by Michael Henderson.
Fine bows will stick in the water less soon than broader ones
and those w i t h very deep V's and get to a higher speed but are more
sensitive to weight forward, which includes the pitching moment o f
the sails. Flat runs aft w i l l pull the transom down by dynamic action
and also delay bow burying.
CoHclusiou. Fine bows and a broad flat run, combined w i t h the
mast being placed further aft (with larger headsails, i f desired) should
reduce bow burying. I t is noted that several accounts of " Mast-aft "
rigs state that the " lift " from the sloping j i b raises the bow b u t the
weight o f the mast aft may have not a little to do w i t h the rising of
the bows. T h e sloping j i b may lift the bows on a reach, especially
if the j i b is boomed but probably has no such effect close hauled.
THE
"ONE-OF-A-KIND"
RACES
T h e principle of these races is that only one of each class o f
boat is allowed to enter i n order that boat shall be pitted against boat,
rather than that helmsmen shall be pitted against each other as w i t h
normal yacht racing. T h e courses are so arranged that tactics play a
small part and the winner of a race can be presumed to have the
fastest boat. There have been several series throughout the w o r l d
this year but the two w h i c h are of most interest to us are those at
M i a m i , Florida and those at Westcliff-on-Sea, Essex.
8
_
Miami, Florida,
February 21-23, 1959.
Yachting and held at the Coral Reef Y . C .
Order of finishing :
1
A Class scow (38 feet long)
2
T I G E R C A T (17 feet long)
3
C O U G A R (18 feet long)
3
(tied) E Class scow
5
FEVER
6
WILDCAT
7
SHEARWATER H I
8
RAVEN
9
MANU KAI
10
FLYING DUTCHMAN
Races sponsored
by
Placing on corrected time :
1 TIGERCAT
2 COUGAR
3 International Canoe.
4 SHEARWATER I I I
5 505
6 A Class scow
7 JOLLY BOAT
7 (tied) W I L D C A T
9 E Class scow
10 F L Y I N G D U T C H M A N
I n these races, the A Class scow usually quickly got a big lead,
followed by the E Class scow, followed by T I G E R C A T and C O U G A R
fighting it out for t h i r d place. These four boats formed the leading
group i n 3 o f the 5 races and all other competitors came i n t w o later
groups.
. _... ,,
The
Boats.
Tigercat was designed by Bob Harris, the former H o n . Sec. o f
the American Section o f the A . Y . R . S . Details o f it are given elsewhere
i n this publication.
Cougar was designed by G . Prout & Sons and is approximately
a S H E A R W A T E R I I . A stock boat was used which had just been
uncrated on the m o r n i n g of the first race and thus was not quite i n
top racing t r i m .
The International
Canoe was sailed by Maestro
Lou Whitman.
Westcliff-on-Sea,
Essex.
September, 1959. Races sponsored
by the Royal Yachting Association and organised by the Thames
Estuary Y . C .
T h i s series of races was entirely confined to catamarans and
was instigated by the R . Y . A . i n order to evaluate them and form a
basis for handicapping.
T h e results of the 6 races are as follows :—
Corrected
1
2
3
5
6
1
3
5
6
4
2 2
1 3
3 4
5 5
7 7
Times :
2 2
1 8
3 5
4 7
5 6
-fr::^;^-:!"
i:^
F R E E D O M . Donald Robertson.
C O U G A R I . Roland Prout.
C O U G A R I I (Fibreglass) K e n Pearce.
S U P E R C A T ( S H E A R W A T E R H I , 1 C.B.
COOL CAT (JUMPAHEAD).
9
4
7
2
7
6
6
7
3
9
8
-
- 9 8 6 11
- 4
4
- 11 12 11 14
10 8 10
1 — 1
SHE GOES (SWIFT).
KITTIWAKE
.:-'r--'••s^,}
BUBBLE (MERCURY)
•
A L B A T R O S S ( S H E A R W A T E R 2 C.B's).
14 S. C A T A M A N N E R
R I V E R C A T (Single handed)
T H A I H I Roderick M a c A l p i n e - D o w n i e
WAVERIDER
- 8 8 9 8 12
R.S. C A T A M A N N E R
- - 11 11 10 13
FLAMINGO.
Cruising catamaran
- - 10 — 12 —
SKAUBA
These races were a t r i u m p h for Donald Robertson, the amateur
and Roderick M a c A l p i n e - D o w n i e who spent some 18 months designing and redesigning his T H A I catamarans.
Members may
remember the model of an early design we had on our stand at the
Boat Show in January, this year. Both are A . Y . R . S . members and
both designed and b u i l t their catamarans themselves.
The
Boats.
Freedom was fully described in A . Y . R . S . N o . 22 C A T A M A R A N S
1958 and is mainly characterized by a good h u l l shape and lightness.
Thai III is described elsewhere i n this publication and has a
shape of h u l l which w-ill appeal to readers as being what they feel is
traditional i n general but w i t h those certain modifications which make
it suitable for a catamaran. A n overhang forward, a low prismatic
coefficient and a flat r u n aft w i t h a wide transom are the main characteristics. V ' d forward sections and a fine entry develop into a
semicircular m a x i m u m section which is aft of amidships, the centre
of the semicircle being above the L . W . L . T h e wide flat transom
drags by about an inch of immersion. T h e structure is most carefully
stressed to give the extreme lightness on w h i c h her speed largely
depended.
Unfortunately, rigging trouble w i t h an experimental
arrangement put her out of a pair of races when i n the lead ; a collision
at the start which carried away a rudder put her out of a t h i r d , and
she was disqualified for being over the line i n a fourth, in w h i c h she
finished first. She also made the fastest timed r u n .
Cougar 1 is a moulded ply 18'6" catamaran by G . Prout and Sons,
Canvey Island, of the same hull shape as the Shearwater I I .
Cougar 2 is almost identical, but w i t h fibreglass hulls.
Cool Cat the Jumpahead, was consistently well sailed and proved
herself only a shade slower than the Shearwater 3, beating her i n
2 races.
"
..
. . .
10
She Goes, the Prouts new 14' Swift of the same hull shape as
the Shearwater, went wonderfully and surprised many by beating the
Shearwater 3, as well as many other larger boats, to take second place
on coriected time in the second race.
Kittiwake,
from Sark, was one of the most interesting boats
present. 16 feet long, she was amateur built w i t h r o u n d bilge hulls
ingeniously made from sheets of flat ply, beautifully built and finished
and extremely stylish. She had very bad luck breaking her mast,
a straight compression failure.
Albatross, the t w i n board Shearwater,
was dogged w i t h troubles.
got two 4th places, but
River Cat, designed by Bill O'Brien and described in A . Y . R . S .
No. 15, C A T A M A R A N D E S I G N , d i d well in the strong winds.
A t times she was unmistakably planing, and travelling very well.
14' Sports Catamanner is a well shaped but heavy
boat which nevertheless went well.
fibreglass
Flamingo, the 36' Prout cruising catamaran described in A . Y . R . S .
No. 2 7 , C R U I S I N G C A T A M A R A N S , and owned by D o n a l d Robertson, went well and w i t h deceptive sedateness, proving as fast to w i n d ward as any, but somewhat inferior d o w n w i n d and reaching.
Bubble is a M E R C U R Y class catamaran, described i n A . Y . R . S .
No. 2 2 o f chine construction for home building. She has never had
a chance to be fully tuned against good racing competition.
Waverider, is a deep V hull sectioned catamaran, I believe.
Skauba.
N o information is available.
THAI
L.O.A.
L.W.L.
Beam
Designeri:
Builders
1 7 ' 6"
16'
8' 6"
J . R.
HI
Weight (stripped) under
Sail Area
2 0 0 lbs.
2 0 0 sq ft.
MACALI'INE-DOWNIE.
: J . R. M A C A I . P I N E - D O W N U ; ,
A p p i n , A r g y l l , Scotland.
T H A I H I is the end product of nine sets of lines, developed from
a previous prototype. She is going into production for the coming
L o n d o n Boat Show and w i l l be available finished, part finished and in
kit form. H u l l s are of fibreglass w i t h m o u l d c d - i n centreplate cases.
Moulded agba hulls are available for those who like varnish.
Modifications are being carried out, i n the light o f racing experience, to improve both her appearance and her performance,
11
12
the least trouble from either traffic or police, for greater convenience
a light, cheap t i p p i n g trailer is being marketed w i t h her to reduce
her effective beam to under 6'.
She is very lively and responsive to sail, and quick i n stays.
Pi-Cal
13
THE
~
LOA
'
'
17'
fry
PI-CAT
CATAMARAN
A R T H U R PivER, M i l l Valley, Calif.
Beam 8'
Draft
(less boards) 9"
-
T o t a l sail area 200'
Pi-Cat is the result of an inability to accept certain apparently
intrinsic limitations i n catamarans.
Manoeuvrability.
I t was felt that the t u r n i n g rate of the craft
should be limited only by the speed w i t h w h i c h the crew can move
across the boat while putting about.
Hull Form.
I t was felt that the traditional destroyer shape now
widely favored could be definitely improved upon. F u l l , round
bows, which cause pounding and pitching, should be replaced by
finer ones more conducive to smoother operation. F u l l bows were
formerly felt necessary to avoid diving of the lee bow. I t was felt
that the answer to this problem was weight distribution, instead of
full bows.
Pi-Cat
has perhaps the most complicated h u l l form yet seen
on a catamaran—possible only w i t h the adaptability of fibreglass. T h e
bow is quite fine, w i t h hollow sections. There is, however, a flare
at the deck line which reduces spray and w h i c h is expected to keep
the boat from d r i v i n g under even when sailed full speed down the
face of breaking seas. T h i s it has so far successfully done.
Forward underwater sections are V ' d in order to present an
easy entrance. T h e form changes to semi-circular just before the
mid-point. T h e semi-circle is continued almost to the stern, where
i n the last foot or so i t changes to an almost flat section at the transom.
T h i s flat section, which is normally above water, prevents pitching
which might be expected w i t h the high degree of rocker w h i c h is a
characteristic o f this particular h u l l . T h e generous rocker aids
manoeuvrability and keeps wetted surface at the m i n i m u m for light
airs.
T o help keep the lee bow from diving, the mast was moved aft
to the mid-point. T h i s resulted i n a large j i b . I n an effort to aid
handling this sail, a balanced j i b boom was used. T h i s was based
on experiments w i t h this arrangement on the 20' trimaran Caper last
year. A report of a similar sail on the catamaran Freedom i n A . Y . R . S .
No. 22 gave further information. As can be seen i n the illustration,
this j i b has a large transparent panel of Mylar film—a common-sense
idea for any fast boat. T h i s particular sail has an adjustable draft
arrangement. W h e n the clew is moved forward and aft to vary the
camber, control lines to the lower guide batten extend and retract
automatically and proportionately. T h e balanced j i b has proven
14
15
most satisfactory. Its use removes much of the p u l l from the j i b
sheet ; i t acts as a b u i l t - i n whisker-pole ; and keeps the fore stay
tight, due to the differential p u l l at the clew.
T h e j i b stay is arranged so it slides across the boat, helping t o
free the j i b from blanketing effects of the mainsail while r i m n i n g .
For broad-reaching, the j i b boom can be slacked forward o f the transverse, and slid to windward of the main, on the opposite side o f the
boat.
Performance of Pi-Cat under favourable conditions is impressive.
She can come about so fast that when the sails start to lutf, the
crew must actually hurl themselves across the craft in order to be
on the proper side when the sails fill on the opposite tack.
Observers
who see her manoeuvre for the first time frequently shout in astonishment.
Pi-Cat
provides an unexpected bonus in that she apparently
rises right up in the water and planes. A surprising amount of stability
is felt when she has but a few feet of the m i d section in the water.
There is no tendency to b u r y the lee bow, and the attitude o f the boat
can be easily altered by merely moving the crew slightly forward
or aft. T h i s ability to plane almost on top of the water, and thus
reduce wetted surface, should make Pi-Cat capable of some surprising
speeds, and a pitot-tube type speedometer has been installed as a
reference.
Pi-Cat's comparative speed around the buoys is not completely
known, as she has never been i n racing t r i m . She was, however,
entered i n the July '59 Pacific Coast M u l t i h u l l Championship Regatta
at San Francisco. Pi-Cat finished t h i r d , betv^een two Shearwaters.
T h e reason this boat has never been put i n racing t r i m may
interest experimental-minded sailors. T h e male mould on w h i c h
the present hulls were cast was made of plastic form in 2 man-days,
w i t h 20 worth of STYROFOAM. Because this was to be an experimental
boat, no particular care was taken to make the m o u l d particularly
smooth. T h e present hulls are quite rough as a result. I t w o u l d be
interesting to learn how much faster this boat w o u l d be i f the hulls
were indeed smooth.
Add
: T H E TRANSPARENT SAIL
N O T E : Since the above was written, we have made some changes
in our transparent jibs.
Because these sails wore out first i n the upper part of the leech
due to luffing, we now use D A C R O N for the upper part o f the sail, w i t h
a large lower window only o f M Y L A R .
16
T h e 17' P I - C A T has the latest version—a balanced j i b w i t i i
horizontal, 3' wide cloths, fully-battened. T h e M A R L A R w i n d o w
is 3' deep and the full w i d t h of the sail. T h i s gives m a x i m u m visibility, but more wear-resistent sail cloth is used above.
T h e M Y L A R windows are no longer cemented i n , but meiely
sewn w i t h wide stitches (1/8'—3/16" apart). A 2" wide M Y L A R strip
is fastened w i t h pressure-sensitive transparent tape near the perimeter
of the M Y L A R panel, overlapping the sail cloth on each side.
After sewing through both thicknesses o f the M Y L A R and the
sail cloth in between, the stitches are covered w i t h strips o f i " M Y L A R
tape i n order to keep the now perforateil film from r i p p i n g .
In the
corners of the panel, where strain might be concentrated, the M Y L A R
is left slightly fuller than elsewhere.
TIGER CAT
L.O.A.
Beam
Draught
Draught C.B's
17' 0"
T o t a l weight, less crew
5301bs.
8' 0"
T o t a l sail area
235 sq. ft.
7f
Measured area
183 sq. ft.
3' 5"
Designer : Bob Harris, 9 Floyd Place, Great Neck, L . I . , N . Y .
Hulls.
These are 3/16th inch moulded plywood covered w i t h
4oz. glass cloth. T h e decks are | inch plywood, faced w i t h phenolic
plastic. T h e centreboards are | inch a l u m i n i u m alloy plate, toed
in 1°. Only one board is d o w n at a time, for example the port board
on the starboard tack and vice versa.
.
,
The Mast.
T h i s is elongated
alloy as is the luff spar.
in section and also a l u m i n i u m
The Production Model.
T h e dimensions of this are the same as
the prototype except for I inch reduction in beam. T h e weight
comes out at 551bs. more. T h e craft is cleverly cast in two pieces,
the upper one comprising the whole top deck and the lower one, the
hulls and the underside o f the bridge deck. "^Phese two pieces are
joined at a flange which also forms part of the spray strips.
T I G E R C A T won the M i a m i O N E - O F - A - K I N D races, beating the
Prout COUGAR SO she must be a very fast boat. T h e production model
must be a little slower than the prototype and we can but see what
the relative performances of the two craft are in future.
17
Tiger
5 April, 1959
Dear John.
K i n d l y accept my sincerest thanks for your congratulatory letter
of 2 0 M a r c h re T I G E R .
A l l o w me to say right off the bat that not one concerned w i t h the
creation of the T I G E R expected that Eric Olsen w o u l d be able to beat
out Roland Prout, not only from the fact that Eric had had little or no
experience sailing the catamaran, but that the designer had himself
so very much to learn as yet about the design of small catamarans. 1
w i l l however venture these comments i n retrospect.
1 . I t was felt by all that the use o f asymetrically shaped centreplates in each hull, both t h i n plates, and using of course but one at a
time, set at an initial angle of incidence to the fore and aft centreline
of the hulls gave T I G E R her first advantage over COUGAR, using thicker
plates, two down, symmetrically shaped. T h i s is probably the
second best advantage, i f it was one at all. We could not prove any
18
of these statements actually unless the boats were tested together in
tanks under exactly controlled similar conditions.
2. T h e greatest advantage Tiger seemed to have was i n the sails.
She was carrying a tremendous roach compared to Cougar, g i v i n g
her not only m u c h more unmeasured sail area, (an inequality i n the
rule) but I suggest that these sails stood better i n spite o f the roach
than the Cougar's.
Besides this there was of course more measured
area.
3. T h e second most important advantage of 'Tiger, and contrary
to the reports you have had is that she had a flatter n m and the aft
sections were fuller, or rather flatter than tliose o f Cougar !
Tigers'
beam at the transom was also bigger. I f she was d o w n by the stern a
bit i t is because the crew was unable to get forward enough to the
designed position due to the fact that the helmsman could not then
reach his tillers effectively. Perhaps it would be more accurate to
say that the extension tillers were not in the best position for this
important measure nor were they long enough.
*
4. For the particular sea and w i n d conditions, 20 to 25 knots
w i n d , w i t h about a two foot to one and one half foot chop I believe
that the greater freeboard and resultant greater height of w i n g off the
water gave Tiger a bit less drag at speed than the Cougar.
There
seemed to be considerably more wetting under the w i n g on Cougar.
There is also the fact that the underside o f Tiger's w i n g is convex,
curved upwards, thus allowing water droplets, (thus weight carried
about) to be run off more quickly. T h i s has something to do w i t h
surface tension of fluids which I vaguely remember from m y physics
class.
5. There is also a fifth and not so obvious a reason for Tiger's
performance which rather sums u p all of these advantages w i t h the
possible exception o f the sails, and h u l l form, that being that Tiger
was built especially as a prototype to meet the competition of the
One of a Kind.
T h a t is to say that in a production model we w o u l d
probably come up w i t h symmetrical smaller centerboards thus losing
I feel some advantage to weather, although even this is inconclusive
since at times Cougar seemed to be doing better to weather than
Tiger on pointing and footing. A n y w a y I must certainly say that
Prout came here w i t h his " stock " model and d i d very excellently
indeed, to w^it that there was so very little difference in their times
and speeds, and not to mention that the Cougar was probably built
at a fraction of the cost of the Tiger.
We are of course planning to produce the Tiger, b u t she w i l l be
all fibreglass, w i t h somewhat lowered w i n g for daysailing comfort,
19
the symmetrical boards to eliminate having to change boards coming
t h r u the w i n d and to make them of less area and weight, total, b u t we
have learned that we w i l l be able to have a somewhat lighter craft,
possibly thus w i n n i n g back some lost advantage otherwise. T h e
h u l l form w i l l be unaltered, as w i l l the sails and the general configuration. We do not expect to lose much i n our stock model, and I
believe that putting this model against Cougar one w i l l see little or no
difference i n their performances.
By the way we had a spray rail on the inboard sides o f the Tiger
and we w i l l keep these besides adding two to the outsides similar to
Cougar, to prevent outside wetting and crew discomfort at high speed.
The centerboards and rudders of the stock model w i l l be of cast
a l u m i n u m alloy, finding that these w i l l have all of the properties of
strength and ductility and anti corrosiveness needed and that they
can be produced more cheaply i n numbers than any other kind at
this w r i t i n g . We also feel in this connection that the thinner plates
are better than the thicker ones, not only from the standpoint of frontal
resistance but from the fact that the centerboard slots may have less
drag where one is using a swinging plate versus a fitted dagger.
The
daggers such as Prout has w i l l always be unpopular in our shoal
waters versus the swing type especially in view of the speeds capable
in these cats.
I hope that these remarks may clarify somewhat the conditions
under which Tiger was able to " eke " out a w i n over her nearest
competition, the Cougar.
I hurry on to say that the Cougar and the
Shearwater were the best looking catamarans at the race, and both
far out performed all other competition. Roland should feel himself
well satisfied in producing two so successful craft, that having met
him my personal regard for h i m is and w i l l always be of the highest
order. I f 1 can handle m y own cat designs someday as well as he
does his then 1 shall only then consider myself of even equal potential.
W e l l that's about the whole story i n the design of Tiger, except
to say that the final proof of the form used in the hulls of Tiger was
accomplished i n the little 9 - foot prototype of the Tiki.
I w o u l d say
that our transom was closer to Freedom's than Cougar's, and so is our
mainsail.
The only regret I have after the One of a Kind is that I d i d not
have more opportunity to talk w i t h Roland. I feel i n h i m as you do
a great friend. I am p r o u d to know h i m ! I also met w i t h Rudy
Choy there and greatly increased m y respect for h i m .
Very Sincerely Yours,
J,^,
,
,
3i;<,
^
20
ROBERT B . H A R R I S .
21
COUGAR
L.O.A. 17'9"
L . W . L . 16'1()"
Beam O . A . 7'11"
Draught, h u l l 8"
Draught, C.B.'s 2'6"
-
T o t a l weight 380 lbs.
Sail area 210 sq. ft., including all
rounds.
( T h i s is the latest sail area and
about 20 sq. ft. more than used i n
Miami).
Designers and builders : G . Prout & Sons, T h e Point, Canvey Island,
Essex.
Price i n America :
approx. $1850.
M o u l d e d plywood, approx. SI700.
(Landed retail prices).
Fibreglass,
Sole agent for America ; Reheats, 2727-29th St., N . W . , Washington,
8, D . C .
. .
T h e Cougar is the modern version of the Shearwater I I and is
made from the same mould as that craft w i t h all the features of light
construction which the Prouts have developed so well, combined w i t h
the strength which comes from the continuous sailing o f Shearwater III
over these last three years.
Hull and Rig Design.
L i t t l e need be said about these as they are
in most respects similar but larger than the Shearwater III, which
most people know already. T h e hulls are of the same shape as those
of Shearwater III, but longer.
Performance.
T h i s is superior to that of the smaller Shearwater
III as regards speed, being a longer boat. I n the M i a m i
One-of-Kind
races, the performance o f a stock Cougar was on a par w i t h that of the
prototype Tiger Cat w h i c h has already been described, though Tiger
won the series. Cougar won the Sea Cliff race against the Tigers
but lost the Presidents Cup to them. A s could be expected from the
hull shape. Cougar is at her best i n moderate winds when she can
beat Tiger.
I n light and heavy going, she appears to be at a slight
disadvantage up to the present. 'The speed of catamarans depends far
more on their weight than the h u l l design and the
Shearwater-CougarSwift hulls are lighter i n weight than most others, though the scantling
af pear to be the same.
22
Wildcat
WILDCAT I I
:
i
L . O . A . 17'9"
Sail area 235 sq. ft.
L . W . L . 16'0"
D e s i g n e r : Seymour Paul.
Beam O.A. 7'11"
Available from :
Beam, hull 1'6"
Dan W . Sanderson,
Construction : Colour impregP.O. Box. 121,
nated
fibreglass.
Costa Mesa, Calif.
23
Wildcat I I must be one o f the fastest catamarans anywhere,
having won the Pt. F e r m i n Race i n the Spring against some very
strong opposition from Hawaiian-type catamarans and
Shearwaters
and also the West Coast One of a Kind Race i n Newport Harbour.
24
She has had a clocked speed of 21 knots average over a 1 mile course.
The Design.
T h e hull shape appears to have a very fine bow,
going into a semi-circle amidships underwater, w i t h a flat r u n ending
in a transom w i t h a rounded lower surface instead of the flatter undersurface of other fast catamarans.
T w i n centerboards are used and
these are placed much farther aft than i n any other catamaran.
The
rig is also placed far aft and the result is probably an ability to keep
the fine bow from b u r y i n g when hard pressed in a beam w i n d .
The
total weight is not given but Wildcat I I appears to be very light.
Sails.
T h e sails shown in the photograph are most beautifully
cut. There is a huge overlap on the j i b and a huge roach on the
mainsail, w i t h the result that the rated sail area is only 176 sq. ft.,
whereas the cloth carried has 235 sq. ft.
CHIQUITA I I
Freeboard 1'5"
Draught I ' l O "
Displacement 585 l b .
Sail area 160 s<]. It.
L . O . A . 16'0'
L . W . L . 15-4"
Beam O.A. 7'6"
Beam (hull) r e Beam (hull W . L . ) 1'2"
Designer, owner and builder : D a v i d Jeffrey.
Readers may remember Chiquita, a 24 foot overall catamaran
designed by David Jefl^rey and described in the Y A C H T I N G M O N T H L Y of January, 1956. She was a hard chined craft designed to
Chiquita
25
II
plane but, though she d i d 14 knots, there was never any indication
that planing had occurred.
T h e latest craft made by this amateur designer is, i n his o w n
words, an " e.vercise in plastics." T h e hulls and most o f the bridge
deck are b u i l t from foamed polystyrene (Polyzote, Expanded Plastics
L t d . , M i t c h a m Road, Croydon). T h i s material weighs only 1 l b .
per cubic foot, comes in slabs 3 foot x 2 foot x 1 | inch thick, can be
easily worked w i t h a saw, knife and sandpaper although a Surform
plane is also useful.
Advantages.
T h e advantages of using expanded polystyrene are
(a) N o m o u l d is needed as i n normal glass fibre boat construction
and therefore a one-off boat can be economically made and (b) T h i s
closed-cell plastic is permanently buoyant, making separate buoyancy
tanks or bags unnecessary. T h e attractive feature of this inherent
buoyancy is that all internal floors are above water level, thus e l i m i n ating completely the need for p u m p i n g or bailing out the bilge water.
T h i s surely is the only boat i n w h i c h i t is possible to d r i l l holes through
the bottom to drain off spray water and not sink i t . T h e floor of each
h u l l is 3 inches above the I ^ . W . L . and two 2 inch holes i n each transom
allow any water shipped to pour out.
After the boat was completely made of foamed plastic and sanded
smooth, it was covered all over w i t h epoxy resin reinforced w i t h glass
cloth. T h i s put a hard and strong skin on the boat and, although
it is only about l / 3 2 n d inch thick, i t makes i t entirely weatherproof
and resistant to wear and tear. T h e resultant catamaran is a little
lighter than the plywood Prout Shearwater and has the advantage of
flexibility of design as no moulds are required. T h e materials cost
about the same.
The Construction.
T h e design is similar to Shearwater III but
to improve diagonal rigidity, cross beams o f 4 inch x 3/8th inch spruce
were sunk into the Polyzote. T h e entire structure has a good feeling
of being " one solid piece."
T h e rounded bottoms are made from the slabs of Polyzote glued
flat on each other up to the floor level, 3 inches above the L . W . L .
T h e top sides are from the slabs placed on edge. T h e Polyzote
surface sands smooth but the texture is open and fibreglassing is needed
for durability and gloss surface.
T h e whole h u l l was quickly made and glued together and i t was
at this stage interesting to have a catamaran weighing less than 100 lbs.
G l u e s . T h e glues recommended by the makers o f the Polyzote
broke along the glue line when edge glued. Aerolite 306, a urea glue,
26
-4:
27
was much stronger and quicker to use. After glueing, a sharp crackling
noise was heard at times. T h i s was shown to be caused by the glue
apparently bursting some small cells. Only a t h i n film of Aerolite
was used which necessitated careful fitting of the parts. W i t h a
liberal application as used w i t h wood for gap filling, there is severe
contraction of the Polyzote.
The Epoxy Coat. T h e resin and glass cloth were put on at one
application i.e. the resin (Araldite L . W . 2 C . I . B . A . ) was poured onto
the sanded Polyzote surface, smoothed w i t h a rubber squeegee and
10 oz. plain weave fibreglass cloth spread on. T h i s was immediately
followed by amber resin, Araldite D for " wetting out " the glass
and a final coat of white L . W . 2 smoothed on. W i t h a workshop
temperature of 60"F. hardening took about two days and this w o u l d
have been longer in damp weather.
Precautions.
T h e epoxy was not found to be disagreeable through
its poisonous properties. Frequent hand washing and barrier cream
were the precautions against dermatitis o f the hands but, even so,
there was some slight fingernail trouble which could have been obviated
by using rubber gloves.
Disadvantages.
Polyzote burns and is dissolved by many solvents-
H o t sunlight can cause the surface to powder. T h e Epoxy is poisonous
and may cause dermatitis. T h e fibreglass-epoxy coat may be dented
by a high localised pressure but it can be walked on safely. T h e under
surface of the decking Polyzote needs to be fibreglassed to get the
necessary strength.
W i t h proper precautions, therefore, there is no difficulty in using
this method of construction. However, the Epoxy coat had ripples
which took 40 to 50 man hours of labour to get off, using an industrial
orbital sander. T h i s was the only serious snag.
Performance.
T h e all up weight is about 260 lbs. ex crew w h i c h
is a little lighter than the plywood version of the Shearwater
III.
T w o fixed keels were used, instead of drop keels. As a result, Chiquita
II is slower on the r u n than Shearwater but is about as fast to windw ard.
Chiquita II had the misfortune to r u n onto some submerged
rocks at over 10 knots, pitching the crew violently forward. T h e only
damage was a slight split i n the fibreglass. Plywood w o u l d not
have withstood this impact so well.
Summary.
Expanded polystyrene, glued w i t h a urea glue and
coated w i t h Epoxy resin appears to be an excellent b o a t b u i l d i n g method.
David Jeffrey is to be congratulated i n being a pioneer i n this field.
Ed.—Reports have been received by me that a quick setting polyester resin can be used w i t h expanded polystyrene. Other workers
have not been able to confirm this and find that the foam dissolves.
SNAP,
A N 18 F T . C A T A M A R A N
by DoN.\LD
ROBERTSON
As a result of a series of experiments carried out on a small
trimaran Fun, I decided to b u i l d another boat. These experiments
convinced me that neither outboard floats nor hydrofoils were the
answer to high speed and having read of the success of the catamaran
Endeavour built by the Prout brothers I ordered a pair of similar cold
moulded hulls.
One reason for not b u i l d i n g a catamaran sooner was that I
live some distance from the sea and w-hereas a trimaran can easily be
made detachable for trailing, a catamaran is a more difficult problem.
Obviously to get the benefit of stability the h u l l centres must have a
big beam in relation to the length of the boat and as soon as these are
made detachable the boat ceases to be one unit and loses its stift'ness.
A further point arises over the m a x i m u m size that can be trailed on
the road not only in beam but in length. I n the case of Snap the length
is 18 ft ; beam overall 9ft. 4 i n . and, w i t h the special trailer I designed.
29
the m a x i m u m road w i d t h w i t h the boat mounted at 60° to the horizontal
is 6ft. 6in. I n m y opinion anything much larger than this is out o f
the question for trailing, apart from the difficulty o f manhandling on
to the trailer. Assuming this is the m a x i m u m practical size for trailing,
any larger catamaran must be strong enough to make a sea passage
— a heavier and different type o f boat altogether.
Having tried out so many different gadgets on Fun, every one o f
which entailed using tools to assemble before each sail I was determined
to keep the new boat simple and to go back to first principles ! T h e
outcome was a non detachable boat w i t h fixed skegs under each h u l l
(i.e. no centreboard) and a straightforward sloop r i g . T h e two rudders
were non lifting.
I n designing the bridge deck I gave Snap 9 i n . clearance above
the water line and a type o f structure which I hoped w o u l d be very
30
stiff. T h e clearance under the bridge deck on a catamaran is a
critical factor i n the design as an increase in clearance increases both
the weight o f the boat and the air resistance. A t sea, Snap's was
found to be adequate except when r u n n i n g when occasionally a sea
would b u i l d up and touch the underneath of the aft part of the bridge
deck ; under the mast where one might expect a wave to hit the
clearance seemed to be sufficient.
O n first sailing Snap it was found that w i t h the skegs, which were
.1ft. by 8in., she reached well and would go about w i t h difficulty b u t
was very poor close hauled especially in a light w i n d . T h e skegs were
removed and lifting centreboards mounted in each h u l l . T h i s i m proved the performance and handling characteristics enormously
but mechanically they were a complication and a constant source of
leaks. T h e water pressure that builds up in the centreboard box is
considerable and the holes through which the lifting wires passed
could not be made watertight.
I t was found that the wooden rudders warped when left i n the
sun. T h i s upset the balance o f the boat by giving weather helm
on one tack and lee helm on the other. L i f t i n g metal plates overcame
this trouble but a positive wire and shock cord had to be fitted to hold
the blades down at speed. Later on larger rudders were fitted not
so much for the improvement i n power but to give better control when
at sea. Rudders have in fact been a constant source of trouble largely
due to trying to save weight and drag, but in any case a catamaran is
very sensitive to directional control.
I n an attempt to increase the speed when reaching some spray
guards were attached to the bow. These were 3ft. long and 4 i n . wide
at their widest point. These were successful as not only was the spray
from the h u l l lee deflected horizontally but the upward reaction gave
considerable lift to the bow.
I think Snap has often touched 18 knots but this is only a guess.
I d i d however cover the half nautical mile in Chichester harbour i n 1
minute and 53 seconds, which is 15.9 knots. G o i n g to w i n d w a r d in a
strong w i n d she was fast and fairly close w i n d e d , but her performance
fell off in moderate and light winds.
/ - , r i' - - »
WIND-CAT
L.O.A. 15'0"
L . W . L . 14' 11"
Beam 7' 0"
H u l l Beams 1'8"
\ - ' y D e p t h o f Hulls 1 ' 2 '
' -"
Draft 2J"
'
Sail Area 83 sq. ft.
Weight (all-up) 150 lbs.
Designer : Finn Andersen, Durban, S. Africa.
31 :
-
'I.:
1)
H U L L DESIGN
^
.^^ .
T h e Wind-Cat, obviously, is designed on the realization that a
catamaran is rarely a planing craft, i n the true sense. T h e weight
factor (—displacement) was therefore receiving top p r i o r i t y .
Second
consideration was a hull-shape, offering the least possible resistance,
yet sufficiently buoyant in the forward sections to reduce h u l l b u r y i n g . . . all w i t h one eye on dryness, and the other eye on windage.
T h e " Fish-shape " was chosen for C . W . L . w i t h a flattish semicircular section. Length/Breadth ratio : 1 : 9 .
T h e 7 ft. long platform carries the revolving cat-rigged mast on
the forward cross-beam, w i t h a central dagger-board slot r u n n i n g its
full length. Given a 3 i n . rocker i t also produces slight additional
lift i n a seaway.
Hulls symmetrical, w i t h centre-lines dead parallel.
2)
CONSTRUCTION.
T h e hulls were built over a m o u l d , w i t h strips o f 3 m m . plywood,
and sheathed w i t h fibre-glass. Internal bracing of hulls effected
w i t h Jin. dia. a l u m i n i u m tubing. T o t a l weight of each h u l l (un-decked)
24 lbs.
T h e perforated platform is slung under the two cross-bars, and
under doublings, fi.xed to inner sides of hulls, offering a central " W e l l "
a few inches below the sitting-out decks.
3)
RIG
T h e 21 ft. mast, made up o f fibreglassed bamboo, is un-stayed ,
and fully revolving. A detachable hooked top gives the sail its characteristic appearance, resembling an aeroplane w i n g , stood on end.
T h e 83 sq. ft. Terylene sail, fitted w i t h a wide pocket, r u n n i n g .
the entire length o f the luff, is slipped over the mast before being
stepped. T h e straight leech and 4 through battens take care o f the
set.
.•
4)
PERFORMANCE
Speed : T h e exceptionally low weight of Wind-Cat permitted
the use o f the small sail area, which, nevertheless, enables her to move
faster than the w i n d on abroad tack and close reach. She moves comfortably at 16-18 knots, and is estimated to have done 22 i n moderate
squalls.
^
As soon as the faired lulf, however, ceases to act as leading edge, as :
in the case before the w i n d , she drops to the speed of other displacement craft.
32
Steering : DifFercntial steering was achieved by simply l i n k i n g
the tillers w i t h a sliding bar, equipped w i t h stops, allowing each rudder
to trail independently, for a certain arc. T h i s principle works very
well indeed, and i t is observed that only the windward rudder actually
contributed to sharp alterations of course, such as going about, the
lee rudder trailing obediently without disturbing the flow o f water.
Lateral Resistance : T h e dagger-board, which can be swung to
varying depths, and also moved fore-and-aft, was originally intended
merely to augment the lateral resistance offered by the hulls, but was
found to be grossly inadequately, particularly at low speeds, as the
shallow-draft, rounded hulls did not provide the expected lateral
resistance. A deeper board is now dealing w i t h the drift at low speeds.
Wetness and Hull-Burying.
I have, as yet, not been able to " fly
a hull " in the Wind-Cat, thanks ( I believe) to the flexible mast, which,
in strong winds, will bend out as much as ,1 - 4 feet at the top, without
any appreciable increase i n the lee h u l l displacement.
For this reason
also, there is no exaggerated bow-wave. T h e hulls seem to slice
through gently, leaving no wake, except from the board, which is also
flexible, and " h u m m i n g " before i t really should.
Whatever bow-wave is worked up in rough water, usually hits
the underside of the platform, which is positioned well forward,
and renders the Wind-Cat amazingly dry.
33
Although she does not b u r y her lee bow, when going hard, there
is a tendency for slicing-in a bit deeper. Sitting her out further out
does not altogether eliminate this short-coming.
Manoeuvrability.
With
the dagger-board
lowered, slightly
forward of balanced position, the Wind-Cat carries just enough helm
to throw her about as easily as a dinghy.
I have found that it pays to sit her well oiU, u n t i l the sail is filled
on the other tack, in order to lighten the hull, describing the larger
arcii. She nevertheless loses most of her speed, when going about.
As for w i n d - w a r d w o r k , the Wind-Cat points as high as any
dinghy, but in most cases, provided there is sufficient water, fewer
and longer tacks, w i t h slightly eased sheet, pay the best dividends.
Overloading.
Designed as a single-hander, for best performance
with a total all-up weight (craft and helmsman) of m a x i m u m 300 lbs.
I t is obvious that the weight of another crew-member w o u l d overtax its dead-weight (or : load to be carried) by 5 0 % . I n fact, even a
small boy o f 50 - 60 lbs. makes the increased drag noticeable.
Criticism.
T h e L . O . A . could well be increased by 1 ft., and
the mast-step moved correspondingly aft, to reduce the tendency to
dip the lee bow, under pressure.
Also, platform could be extended, allowing helmsman to sit her
out further aft.
fioom could be raised 6 i n . , merely for the comfort o f helmsman.
T h e profile would benefit in appearance, from lifting the sheer
forward (at present parallel to W . L . ) .
A means devised for hoisting and lowering sail, w i t h o u t having
to step and un-step the whole rig, and yet maintaining the mastfairing, that the sleeve provides.
I t is doubtful whether any further reduction in weight w o u l d be
possible, without affecting the .strength generally, and torque i n
particular.
.\TTUNGA ^
by
PiriKR
HOOKS,
20 F T . S A I L I N G
43 Comer
CATAMARAN
Street, Brighton, Victoria, Australia
T h i s design represents the s u m m i n g up and consolidation o f
4 years' experience w i t h an experimental 20 ft. catamaran w h i c h was
modified extensively year by year as various arrangements o f fins,
hull shapes etc. were tried out.
T h e prototype boat built exactly to the plans has proved to be
an outstanding success, particularly i n hard winds.
Attunga
T h e yardstick for catamaran performance i n Port Phillip is the
racing fleet of ten Yvonnes, w h i c h includes the National Champion,
Duet, at Sandringham Yacht C l u b . Attunga
has not had many
opportunities of racing consistently w i t h this fleet as they are quite
naturally a keen group racing for an aggregate prize and should not
35
suffer interference from another boat on their course.
However,
on the occasions when Attunga has been able to participate i n open
events she has won them all, except three drifting matches soon
after launching, when still untuned.
T h e most recent w i n was the " A n n u a l Catamaran Classic " ,
which is a race open to all catamarans, held at Sandringham. T h i s
race, sailed i n a stiff northerly w h i c h had all crews swinging and
weathering hulls lifting well out i n the puffs, showed Attunga's potential
very well. T h e fleet consisted of ten Yvonnes, some Quickcats,
Charles Cunningham's new 20 ft. fibreglass Austral 20 (complete
w i t h swing planks), and Attunga.
T h e course was triangular of about 15 miles total, w i t h a work
from the start to the w i n d w a r d mark, a close reach, a r u n , and a work
back through the line, 3 times round. Attunga included a flag buoy
300 yards to w i n d w a r d o f the correct w i n d w a r d mark on the first
round, as d i d 3 other Yvonnes and the Cunningham designed fibreglass
20 foot, d i d not use the spinnaker on the first two runs, and still w o n
comfortably by 4 minutes. W e l l sailed, the race could have been
won by 15 minutes on an elapsed time of 1 hr. 50 m i n .
Most of the lead was established on the w i n d w a r d legs, some on
the close reaches, and of course ground was lost on two o f the runs
(in the first round Attunga was passed on the r u n near the lee marks
by 3 Yvonnes and the Cunningham 20 footer, all w i t h spinnakers
set). O n the first long work to w i n d w a r d through the line, Attunga
opened up a big lead and was never seriously threatened thereafter.
On the t h i r d r u n d o w n w i n d , the spinnaker was set to ensure that the
lead already established was not diminished.
Attiinga makes several radical departures from what has become
somewhat commonly accepted practice i n catamaran design and
performance both in this country and overseas, namely :—
1. T h e boat is quickly demountable into 2 equal and opposite
halves down the m i d line of the bridge deck, both halves are locked
together by 4 stainless steel shear pins passing through holes i n the
ends of overlapping stainless steel fangs, like chainplates, w h i c h are
screwed to the ends o f the main beams where they are cut along the
mid line. T h i s device is very strong, but simple, and is similar to
the type of locking used in the folding wings of carrier borne aircraft.
However, it is believed that Attunga is the first catamaran design
which uses the system for demounting down the centre line. Both
halves, placed deck to deck, fit comfortably on a normal trailer, w i t h
all the load contained between the wheels. Kach half is a very easy
lift for two weedy specimens.
2. T h e overall beam is wider than usual, 10 ft. 0 i n . on an
overall length of 20 ft. 0 i n . T h i s feature produces enormous power
to drive the boat hard, w i t h consequent brilliant performance to
windward in a strong breeze. T h e cockpit, 9 ft. 0 i n . wide and 8
ft. 0 i n . long, allows plenty o f space for sunbathing etc. when day
sailing and w i l l allow a small shelter, or doghouse, 6 ft. 0 i n . wide
by 4 ft. 0 i n . long to be placed on the deck for sleeping, or as a refuge
for children away from strong cold winds.
,1. T h e hulls are wider and flatter than usual (2 ft. 2 i n . compared
w i t h the average of about 1 ft. 6 i n . for comparable length), and are
of the disappearing chine type, something like the Darkie shape
fined out and without the
flare.
--"
'
4. T h e boat really planes ; one has the impression when reaching at about 20 knots on one h u l l that more than half the total weight
is supported dynamically, because the lee bow is well out and only
about two thirds of the lee h u l l is i n the water, and the transom leaves
a hard, flat wake. I n consei|uence o f the hull shape, the lee bow
always lifts to the steep seas of Port Phillip and has never buried.
It is safe to say that Attunga is completely free of the appalling characteristic of the nose-dive w h i c h has hitherto been not at all u n k n o w n
in catamarans.
Similarly, Attunga does not suffer from the i n f u r i ating habit of " hobby horsing " i n a seaway.
5. Attunga is extremely fast i n stays, coming about i n a similar
time to that taken by a Payne M o r t l o c k Canoe. Perhaps the fast
tacking is due to the shape o f the hulls and disposition o f r i g ; when
38
tacking the sterns sweep across the top of the water as the helm is
put down. I t is quite unnecessary to back the j i b or to jerk the main
boom to windward, as in common practice with deep hulled catamarans.
6. T w i n fins provide plenty of " bite " for windward work
and even when one hull is skipping, can be adjusted to a nicety on a
reach, and be drawn up completely when on a run or when beaching.
A handy feature is that the fin cases are offset on the inboard side
of the keels, which makes them easy to construct, and leaves a c o n tinuous running surface for beaching. T h e t w i n fins are a great
improvement over the single central fin which we had for one season
in the experimental boat. T h i s fin had perforce to be 7 ft. 0 i n .
long in order to reach anywhere near sufficient lateral plane area,
and in consequence exerted a great overturning moment on the boat.
The fins in the prototype project only 3 ft. 0 i n . below the keel and
the boat is therefore very stiff. T h e cases are long enough to allow
the fins to fold well back in the event of grounding, where their profile
is such that the main force against the back of the case is an upward
one. T h u s the virtue of the simplicity of the dagger fin is partly
combined w i t h the safety margin and range of adjustment of the
fully swinging fin, in a relatively short case.
7. A building j i g is not required. Four plywood side panels
are cut to the finished shape, chines are attached to the inboard sides
and gunwales to the outboard sides. Opposite pairs of sides are
placed over two levelled trestles, the frames inserted where marked
on the panels, the keel drawn over, fin cases built i n , keel and chinesfaired off, bottom skinned, the assembly turned over and the deck
applied in one panel. A l l curves are so easy that the side panels fit
around the frames nicely, somewhat after the manner of b u i l d i n g
the fuselage of a model aeroplane.
Final connection of the two hulls is uncomplicated, as the two
crossbeams fix directly to cleats projecting through the deck.
T h e mast is a modified box section, which is very suitable for
amateur construction, as is indeed the whole boat which can be put
together from the cheapest of materials, by any amateur.
I t is i n teresting to note that Attunga is much lighter than another catamaran
of similar size built of fibreglass, and, being constructed o f wood,
is quite unsinkable in any circumstances. A l l the materials, including
Terylene working sails at £AH?i, cost approximately j{jA250. A
spinnaker would cost about £20.
8. T h e prototype Attunga
has been subjected to a series o f
sailing tests and inspections o f the structure by members of the committee of the Australian Catamaran Association, most of w h o m are
39
keen saik)is of the now well-known Yvonne type. T h e general
committee passed a motion on the 14th A p r i l to the effect that the
Attunga has now been declared an approved design, and thereby
receives the full approval of the Association. T h e rating " A . C . A .
approved Design " ensures that the boat is structurally sound, handles
well and gives good performance.
Attunga is the first design to
receive a full rating under this comparatively new Association R u l i n g .
Fortunately, the Committee had only to consider the structure and
handling characteristics.
A point was raised at the meeting that, unlike narrow beam
catamarans, there is as yet no definite information as to whether or
not the boat is rightable. N o false claims are made for the design
on this point ; it is the designer's opinion that, i f capsized, Attunga
would be difficult to right again w i t h o u t some assistance. T h e crew
would stand on the lower fin w i t h the boat on its side u n t i l assistance
could be rendered.
W h e n the mast can be raised parallel to and
above the water the weight o f the crew on the fin would almost certainly
right the boat.
T h e fully detailed w o r k i n g plans, which include full size profiles
of critical parts, have been drawn up w i t h a view to fostering an
.\ustralia wide class. Weights w i l l be laid down when all the components of the existing prototype boat have been weighed i n the
fully dry state, w h i c h w i l l serve as a guide for establishing m i n i m u m
weights slightly below that of the prototype.
SWIFT
L.O.A. 14'6"
Weight 225 lbs. rigged.
Beam 6' 0"
Sail area 120 sq. ft.
Draught ex. C.B. 7"
Mast length 18' 3"
Draught C.B. 1' 9"
Designers : G . Prout & Sons, T h e Point, Canvey Island, Essex.
Price : ^165.
T h e Swift catamaran was only introduced by the Prouts at the
Boat Show in January this year (1959) and already has been adopted
by many sailing clubs as class boats and w i l l soon be seen in most
sailing waters.
The Design. T h e smaller the catamaran, the greater the relative
sail area which can be carried as compared to the weight and wetted
surface.
For this reason, the Swift is not so very much slower than
her larger sister. Shearwater III.
I n fact, at the O N E O F A K I N D
races at Westcliff-on-Sea, Essex, i n one race Swift beat both the
Shearwater III and Jumpahead.
40 >
nice roomy cockpit and an increased efficiency to tiie mainsail by
straightening its vertical axis. A t the same time, the extra " sweepback " to the j i b must decrease its drive but this is apparently of little
moment i n view of the above race results.
Summary.
T h e Swift is a fast and comfortable catamaran o f a
more popular size than the larger ones. I f capsized, she is easy to
right single handed.
SHAMROCK
L . O . A . 22' 0"
L . W . L . 19' y
Beam O.A. 12' 8"
Draught 1' 4"
Sail Area 241 sq. ft. ( M a i n S.L.
144, Genoa 97).
Displacement l . , l tons.
Accommodation 4 b e r t h .
Designer : Bill O ' B r i e n A . I . N . A .
Makers : Hawker Siddeley Hamble L t d .
T h i s attractive hard chine catamaran is designed as a t w i n hulled
motor sailer without a centreboard. Comfort and safety are given
priority rather than speed but she w i l l do her 10 to 12 knots i n a
force 6 w i n d w i t h no tendency to lift the weather h u l l . However,
all the weights are low down i n the hulls and, should she be t h r o w n
over in a gale, she should right herself from a mast-horizontal position.
T h e design is a reduction o f a 26 ft. catamaran w h i c h was originally
designed for an A . Y . R . S . member.
Accommodation.
There are four berths b u t two extra can be
slept, i f necessary. T h e galley is 7 ft. long w i t h standing headroom
in each hull. T h e toilet is a " Baby M i n o r . "
Sailing.
As in all catamarans, there is virtually no heel and this
w i l l be the main attraction of the craft. She tacks smoothly and
quickly w i t h the j i b let fly in normal keel boat fashion. T h e r e is
wheel steering coupled to tillers for ease o f handling as she w i l l stay
on course when set. T h e absence o f centreboard w i l l be a great
boon for sailing in shallows and it is one of the features o f the hull
shapes produced by Bill O'Brien that they have a surprising amount
of lateral resistance compared to rounded sections. D r o p rudders
are used.
Motor.
T h e 18 h.p. Evinrude gives 8 to 10 knots w i t h o u t undue
noise and is easily retractable for sailing.
Photographs : T O N Y H O O K , Southern Evening Echo, Southampton.
Summary.
Shamrock is about the right size, has wonderful qualities
and no vices. She should be ideal for longshore sailing for a family
4.3
Shamrock
man. There is a hatch i n the hridgcdeck floor and a keen angler can
fish without even getting out of bed. What more could one want ?
44
HURRlCANIi;
L . O . A . 12' 6"
Beam O.A. 5 ' 6 "
Draught 6"
Draught C.B's 1' 9"
Weight : 150 lbs.
Sail Area : 115 s q . f t .
Designer : Jack Blundell, Sandhills, St. Catherines Road, H a y l i n g
Island, Hants.
Background.
Jack Blundell bought one o f the first Shearzvater
lITs
i n 1955 {Zoomph I) followed by another in 1956 w h i c h was
borrowed on one occasion by H . R . l l . I'rince P i i i l i p . He tried out
the prototype Bell Cat designed by IJffa l-'ox in 1958 but found them
all too heavy to manage single handed and designed a smaller, lighter
12 ft. catamaran w i t h the deep V sections of the Bell Cat and w i t h o u t
centreboards.
Performance of the 12 ft. deep V. T h i s little catamaran had under
100 sq. ft. of sail area but was sailed by Jack around the Isle of W i g h t ,
some 60 miles i n ten hours, quite a remarkable feat. However, the
light weather performance suffered for want of dagger boards and
when driven hard, the lee hull buried. These faults were corrected
by raising the bows 3 ins. at the stem, lengthening the mast from 15 ft.
to 18 f t . , increasing the sail area to 115 sq. ft. and b r i n g i n g it aft 6 ins.
T w o small dagger boards were added. Performance was then found
to be on a par w i t h the 12 ft. 6 i n . River Cat.
The Hurricane.
'I'he shape of this hull is a V forward which is
slightly deeper than a right angle, sweeping back through a semicircle to a U-shaped transom. T h i s should go well i f the weight is
right. Indeed, the whole design is very carefully and astutely done
and should produce a good boat.
Jack Blundell w i l l shortly be producing these hulls in fibrcglass
for sale at £\9 each with built in dagger board casings. For those
who may wish to finish the craft off to the designer's plans, the balance
of the wooden parts w i l l cost £ 1 8 , the plans and instructions £2-2-Q
and wooden mast and boom planks £,\0.
The Hurricane Class.
Jack believes that a large number of people
want to experiment w i t h catamarans and this cannot but fail to be
good for development in addition to the great fun to be derived by
backing ones ideas. For this reason, the Hurricane ('lass w i l l only
have three restrictions : 1. T h e hulls to he from the designers moulds.
2. T h e sails to have the Hurricane insignia and 3. T h e length overall
to be no more than 12 ft. 6ins. However, one would think that some
restriction on sail area would be necessary to avoid complicated handicapping systems.
For the 1960 season, the designer proposes to hold one meeting
for any catamaran 13 ft. or under w i t h a £25 cash prize for the winner.
TAMAHINE
L.O.A 1 2 ' 0 "
L . W . I , . 11' 3"
Beam O.A. 7' 0"
Designer : John M o r w o o d .
Beam, hull r 6"
Displacement 267 lbs.
Sail area 110 sq. ft.
Amateur builders ; John Acton ( N o . 1), Geoff D u m b l e ( N o . 2).
Readers may remember the Tamahine design of publication N o .
18 which was made from five strips of plywood tacked together at the
corners. T h i s design has been made by John Acton and also (Jeoff
Dumble as two separate boats. I n both cases, the hull construction
produced no great difficulties which was the main object of the design
47
but the sailing reports are so full of interesting points which have a
bearing on catamaran design and rigging that they should be studied
w i t h care.
Jo/;// Acton's Report No. 1 : " I was rather concerned that
Tamahine's rocker might make her rather unstable fore and aft, but
this is not the case, though the sitting position on her is fairly critical
if drag from the transom is to be avoided. Having had to experiment
w i t h weight distribution, I made up a platform to sit on which is
absurdly heavy (being made of materials 1 already had). T h e hulls
weigh .SO lbs. each and the tubular steel cross-frame weighs 26 lbs.
and is highly successful, being dead rigid and enabling the two hulls
to be dismantled for transport, though I have also adapted my trailer
w i t h rollers to take the keels so though she can be rolled up on to the
trailer and launched w i t h ease. T h i s arrangement is highly successful
as one person can handle her in this way w i t h no difficulty.
• '
Rig. " Since I already had an IS ft. mast, I tlecided to have a
Bermuda type o f r i g which has the advantage of being able to back
the jib to assist going about.
" I think the h u l l design is excellent b u t i t is not getting a square
deal as a result of heavy equipment and too small sail area. I am
sure she w i l l be very fast. She goes about easily. I should like you
to know how pleased I am w i t h your design, which suits my particular
purpose ideally."
Report No. 2, John Acton : " I have now^ done a good more
sailing i n m y Tamahine.
Although I have not got a speedometer
and therefore cannot give actual speeds, I can say that she is faster
than dinghies in light winds but not appreciably so i n moderate
winds. I n fresh winds, however, when she planes readily, she will
go at least 5 0 % faster than an Knterprise or G.P. 14.
" T h e above performance is w i t h one up. T h e additional weight
o f a crew has the effect of slowing her down considerably and making
it almost impossible to rise on to a plane.
" I t is necessary in light winds to move forward to avoid transom
drag, but i f you remain forward in a moderate to fresh w i n d , she w i l l
plane along satisfactorily but will dig in her bows from time to time
and occasionally w i l l stop dead. T h i s is a most alarming t h i n g and
I suspect it may be a sort of frustrated forward capsize. However, i f
one moves back a little, she w i l l lift her bows up, showing perhaps
18 inches of daylight forward and go like a train. She goes about
easily and needs very little board. Her centre o f lateral resistance
seems to be further forward than is relatively the case w i t h larger cats
but perhaps this is to do w i t h crew weight distribution.
48
" T h e only respect in which Taiiuiliiiiv falls short of my requirements is her limited carrying capacity. 1 have therefore been considering building a larger one, perhaps 14 ft. or 14 ft. 6 i n . , or halfway
between Tamahine and Tuahine.
" M y only anxiety about a large midships section to reduce
wetted surface to a m i n i m u m is that it entails rather a sharper run
to the stern which I think tends (on Tamahine at any rate) to p u l l the
stern down and lift the bows when planing, thus making a shorter
and more sharply curved boat than would be the case i f she rode
along on her full length.
" I t occurs to me that a good way of comparing the beha\iour o f
right angled sectioned hulls w i t h that of round sections would be to
construct a right angled h u l l w i t h exactly the same distribution of
buoyancy as that of an existing design, such as the Prout Swiff.
I
would be prepared to do this i f the figures are available, though of
course the buoyancy would vary according to the degree of immersion
of the hulls. Nevertheless, an approximate parallel could be drawn.
Having built Taniahine, I do feel that in a 14 footer 1 would like
rather less rocker."
Geoff Dumble's Report : " We now have iier on a fairly large gravel
pit near here where the w i n d is reasonably steady. As you w i l l see,
she has a " Solo " sail o f 90 sq. ft. N o t really large enough but she
does motor along i f the w i n d is reasonably strong. T h e lee bow
Tamahine : Geoff
49
Dumble
tends to bury, I find, and would probably sail itself under in really
gale conditions.
" Going about is quite fair p r o v i d i n g I remember that she is a
cat and do not shove over the tiller too quickly ( I have an 11 ft. dinghy
as well and sometimes forget which one I ' m sailing !) She has a
smallish centreboard (not dagger) but this doesn't really make a lot
of difference one way or another.
" She carries a fair amount of weather helm in a blow so I mostly
hold the tiller w i t h m y foot and then have two hands for the sheet.
I've put a thrce-to-one purchase on the sheet now in place of the 2
to 1, but she still takes a bit of holding.
" For next season, I shall probably step the mast back and fit a
j i b . However, I do feel that the m i n i m u m length for a reasonable cat
is probably nearer 14 than 12 ft. I t could be that Prouts are right
after all ! "
Comment : \. 9 i n . rocker on a 12 ft. boat does not seem excessive, especially as the point at the keel contributes very little to
rocker effect. However, as John Acton points out, this shape does
tend to throw the bow up and a model trimaran I once made w i t h
floats of this shape w h i c h pivoted used to go along w i t h the floats
cocked up at an angle o f about 30". T h e main fault w i t h Tamahine
here is in the fineness of the stern, which would have been better
w i t h a wider and flatter transom.
2. Speed w o u l d be increased by (1) reducing the beam to 5 ft.,
(2) flattening the transom and making it wider and (3) by lighter
construction.
3. T h e " frustrated forward capsize " is most interesting and
shows the necessity of correct crew placing in any catamaran. T h e
sudden stopping is due to the immersion of the vertical stems and a
resultant bad shape for resistance combined w i t h raising o f the sterns
probably out of water producing a short waterline length.
4. T h e absence of bow burning w i t h the weight i n the correct
place i n John Acton's craft and its presence in Geoff Dumble's boat
w i t h about the same crew placing indicates that it is due to the mast
being so far forward.
5. Excessive w^eather helm such as Geoff D u m b l e has slows any
boat very much but has more effect on a catamaran, especially one
w i t h even a right angled V which is far more stable in yaw than a
rounded sectioned h u l l .
6. Both reports indicate that Tamahine is too small for the
members concerned but this objection only applies to the craft i n
50
question. W i t h the same hull profile and wider hulls aft more buoyancy w o u l d be added where i t is needed, fore and aft stability w o u l d
increase as would top and m e d i u m speeds.
Lighter construction and reduced beam w o u l d allow more weight
to be carried. I t would be a pity i f 12 ft. catamarans were found
to be too small for two persons.
14 F T . S P O R T S
CATAMANNER
L . O . A . 14'
Weight 320 lbs.
Beam 7'
-^^a^ft #
Sail area 145 sq. ft.
Draught 7"
Construction : Fibreglass.
Designer : l u i c k Manners, 9.1, Ridgcway, Westcliff, Ivssex.
Builders : T w i n Hulls L t d . , 50a, Salisbury A v e . , Southend, I'^ssex.
T h i s is a nicely shaped hull with a fine entrance developing in to
a rounded midships section and a flat run. T h e hulls are symmetrical
and their tops form seats at the side of the bridge deck so that when
sailing, one does not sit i n a " saucer full o f water " as happens w i t h
most designs. I t is a handsome craft, nicely finished i n the model I
have seen.
T h e fibreglass construction means easy maintenance and, by
undoing ten bolts, both hulls detach for ease o f storage. T h e craft
is available as a k i t w i t h the hulls already moulded.
14 F T . R A C E R C A T A M A N N E R
T h i s craft is exactly the same shape as the " Sports " Catamanner
but the hulls are moulded plywood w h i c h makes them lighter and
there are t w i n centreboards.
18 F T . 6 I N . C A T A M A N N E R
L . O . A . 18' 6"
Sail area 200 sq. ft.
Beam 8' 0"
Construction : moulded plywood.
Draught 8"
Fibreglass sheathing optional.
T h i s craft is designed along the same general lines as the " Sports
Catamanner " and looks a nice craft. N o details o f performance
relative to other craft are available.
Comment : These three craft have all got good h u l l shapes and,
in the models I have seen the construction and finish seem excellent.
T h e C A T A M A N N E R range are seldom raced as most of them are
fibreglassed and heavier than the pure racing types. However, they
must make excellent family boats where their stability and fibreglass
construction are valuable.
SI
1 8 / / . 6 in. De Luxe
A RETRACTABLE
Calamanner
UNDERCARRIAGE
BY M A J O R GENERAL H . J.
PARHAM.
T h e craft has Shearwater I hulls shortened to 15 feet w i t h a ho.x
spar lying fore and aft amidships to take torsion w i t h a cross spar at
its fore and aft ends. Below the bridge, a steel tube ( A ) runs from
one h u l l to the other through two plates bolted to the box spar. O n
this tube, both the wheels and centreboard are mounted. T h i s tube
does not rotate and its ends fit into cup shaped wooden pieces glued
to the main faces of the hulls in order to steady them.
The Centreboard.
T h e centreboard is a little offset from the
middle line and is mounted at one end of a collar which rotates on the
steel tube (A). A flat steel strip runs from the other end of the collar
to a little way along the board to help w i t h the side strains when sailing.
O n either side of the collar, t w o metal plates run upwards to be bolted
to the central box spar of the catamaran. T h e board is raised by a
short rope cleated on the deck and kept down by a bungec to the front
cross bar of the bridge.
The Wheels. These are made of hard wood soaked in oil w i t i i
slightly larger plywood sides to keep on the tyres made of rope wound
around them. A I inch axle passes through each and is secured
through holes i n light alloy angle pieces at each side.
. .
53
The Legs.
These are composed of the hght alloy angle pieces
carrying the axle of the wheel and these alloy pieces are bolted to
shallow box spars w i t h plywood faces. A t the top of each box,
two bent metal loops pass over the athwartships tube ( A ) to form
bearings on w h i c h each undercarriage leg can swing backwards or
forwards.
The Radius Rods.
Each wheel is retracted by a " Radius rod "
of L section. A t the lower end, i t pivots on a bolt near the main
wheel axle and, when the wheel is down, it passes upwards and forward between two guides under the forebeam of the bridge deck.
T h e guides are joined below the radius rod by a bolt and a notch i n
the radius rod slips into this bolt to hold the wheel i n the " d o w n "
position. A weighted handle holds the radius rod i n position on the
bolt.
Retraction.
Each wheel is lifted separately. T h e handle of the
radius rod is lifted an inch or so to free the notch from the retaining
bolt and it is then drawn forward, lifting the wheel. I t is kept i n the
" up " position by the weight of the handle.
Lowering. T h e wheel is lowered by lifting the handle of the
radius rod. T h e weight of the wheel then pulls it down t i l l the bolt
below the guides enters the notch, so making the assembly r i g i d .
Summary.
I have found this system a perfect Godsend. I t has
given no trouble and the boat has been out 77 days this season (1957).
T h e catamaran balances nicely when the wheels are down so that i t
w i l l rest either on its bow or its stern and one can walk on deck when
on the wheels. By a lucky fluke, the concentrically mounted centreboard bearing also gives correct balance to the boat when sailing.
T h e wheels are very elementary but the oiled " hardwood on bolt "
bearing are excellent, needing no oiling or attention d u r i n g an entire
season.
LETTER
Sir,
Congratulations are due to you people i n the L o n g Island area
for your strenuous work in organizing an American Section o f the
A . Y . R . S . I enclose a small contribution towards your research fund
and hope others can see fit to assist you i n getting systematic experimental test work underway.
I represent a 3-family syndicate which has had a strenuous and
pleasant summer completing the final 6 0 % o f a Hawaiian type catamaran which we hopefully named Scat, from a design by Rudy Choy
and Warren Seaman. T h e design is intended for local ocean racing
55
Scat
in prevailing light winds, w i t h roller reefing w h i c h we hope w i l l
permit us to keep going i n a blow.
Her measurements are the
following :
L.O.A. 2 7 '
L . W . L . 22'
Beam 9' 8"
• •
Draught 1 '
'
^'"
Mast height above deck 35'5"
Sail Area (Genoa) 520 sq. ft.
Displacement 1050 l b .
Fabrication follows modern Hawaiian practice, i.e., light spruce
frames and stringers covered w i t h I i n . plywood skin, forced into
m i l d compound curves by a remarkable combination of wetting and
brute force. Difficult fillets and the h u l l ends were laminated from
Styrafoam and hand shaped. A layer of fibreglass, doubled at critical
points, converted the somewhat elastic w i n g - h u l l assembly into a
rigid, skin stressed structure.
D u r i n g two months o f shakedown sailing. Seal has shown promising light weather [ability, ghosting along easily past all informal competition as had been hoped from her large r i g , specialised for Southern
56
Californian winds. Her catamaran sluggishness i n coming about
occasionally gives revenge to the large keel sloops in tacking up narrow
channels. A t first we were somewhat discouraged by tiie tendency
to go into irons and by the inferior ability to point to windward in
light airs. However, both defects have almost vanished as the crews
gained experience w i t h the boat.
• A local catamaran racing club was recently organized, resulting
in an initial Christmas race involving three smaller catamarans and
ours. I n the first race, a 14 mile course inside and outside N e w p o r t
Harbour w i t h a light breeze averaging 5 m . p . h . . Scat took a first,
followed in 12 minutes by W a l t H a l l , a former international Snipe
champion, sailing liis modified Slieancater III w i t i i dagger boartis
and 175 sq. ft. Thistle r i g w i t h obvious skill which had our crew
sweating to hold the larger boat's lead. T h e second race was similar
w i t h the breeze slightly stronger i n w h i c h H a l l was nosed out of
second place by an otlier 16 footer, the Black Cat, designed by Seymour
Paul along modified Shearicater
lines, again w i t h Thistle r i g and
daggerboards. T h e men on the little cats were surprised at being
out-ghosted by a big cat carrying a 4 man crew, but they promise to
" suck us up their exhaust pipes " on our next encounter i n a w i n d y ,
sheltered body of water near L o n g Beach i n February.
Some tentative comments regarding the mystical qualities of our
asymmetrical hulls without daggerboards may be of interest. W h i l e
I share the scepticism o f other A . Y . R . S . writers, sailing experience
has shown that i f we hike to leeward i n light airs, getting the weather
hull up on the surface as much as possible, then the deeply immersed
and asymmetric lee h u l l points quite decently w i t h o u t excessive yaw
angle t h r u the water. I n strong breezes, the boat rolls to lift the
weather h u l l clear of the water w i t h four o f us hiking to w i n d w a r d
and again the immersed lee h u l l gives good w i n d w a r d performance.
Our best speed to date was 15 m.p.h. by an " Airguide " commercial
pitot tube instrument, sailing fairly close hauled w i t h the weather
hull out, the w i n d being 15 to 20 m.p.h. Bearing off caused us to
slow down, suggesting that more w i n d and a broader tack m i g h t
provide a b i t more speed (or an upset).
T h e question remains open whether the total h u l l drag when
close hauled might be reduced by p u t t i n g all the sideforce on a yawed
daggerboard of decent aspect ratio, as an attempt to reduce underwater induced drag. W e expect to t r y this experiment on our first
haulout.
Despite the wetted surface argument, the Hawaiian deep V sections
57
at bow and stern appear to generate less wave fuss than the fuller
Shearwater sections, at low and higher speed.
Warren Seaman tells us that
down the face of following seas,
each h u l l during rolling serves to
into a spinnaker knockdown — a
sloops and, he says, symmetrical
yet sailed in these conditions.
d u r i n g high speed spinnaker runs
the outward t u r n i n g tendency of
counteract the tendency to broach
danger common to conventional
hulled catamarans. Scat has not
• > .;- r>c,
i-r;j,-ii
i
T h e above comments are intended to
that Rudy Choy and his predecessors
arrived at a surjirisingiy good calaiTiaran
Still, large improvements are certainly
A . Y . R . S . people.
convey our g r o w i n g suspicion
in Hawaii have empirically
hull design for ocean sailing.
i n store t h r u the efforts of
FRED C .
3689 N . Fair Oaks, Altadena, Calif.
GUNTHER.
BUILD YOUR OWN
CATAMARAN
THIS WINTER
-
There is more to a successful Catamaran than just twin
hulls. Over five years' experimental work culminating in
severe tests have produced the P R O U T Shearwater
Catamaran which has sailed with such outstanding results
that over 700 sail numbers have been registered i n the new
Class.
Why not build your own ready for next summer?
PROUT
SHEARWATER III
and 14 6 SWIFT
CATAMARANS
SHEARWATER I I I
complete less sails : £214
Ex Works.
SHEARWATER K I T
complete less sails : £129-16-0
SWIFT
14' 6- CATAMARAN
complete less sails : £165
Ex Works.
SWIFT K I T
complete less sails : £98
A l l kits are complete wUh a
fittings, and supplied with hulls
moulded, sanded for paint.
G.
PROUT
Photograph by
courtesy of
" Lillrput"
magazine
& SONS L T D .
THE POINT, CANVEY ISLAND, ESSEX.
Telephone Canvey
190
SEE the CATAMANNER
TWIN HULL BOATS AND KITS
on stand D. 12 of the EARLS COURT BOAT SHOW
The pioneer and specialist catamarans builders T w i n H u l l L t d . ,
produce the f o l l o w i n g standardized classes f r o m the designs o f
E r i c k J. M a n n e r s t o suit different requirements :—•
FOR VERSATILITY
l i f t . C a r - C a t Class. The 1 c w t . catamaran designed t o travel anywhere on the average car t o p . Complete or as k i t w i t h hulls f r o m £ 7 4 .
FOR C O M F O R T .
14ft. Family class.' Designed p r i m a r i l y f o r safety and c o m f o r t .
V i r t u a l l y uncapsizable and unsinkable w i t h 6 water t i g h t c o m p a r t ments. C o m p l e t e or as k i t w i t h glass-fibre hulls.
<
FOR S P E E D
14ft Sports or Racer class. T h e Sports model has glass-fibre detachable hulls. A v a i l a b l e complete or as a k i t . T h e Racer has n o n detachable hulls and is a very fast boat. F i t t e d w i t h l i g h t a l l o y spars.
FOR L U X U R Y
18ft. 6in. class Catamanner i n t r o d u c e d 1957 as a racer o r de-luxe
cruiser.
FOR Y O U
W r i t e for fully illustrated brochure.
TWIN
HULLS
LTD.
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